Cylinder identifying system for internal combustion engine

ABSTRACT

A cylinder identifying system for an internal combustion engine enables fuel injection and ignition controls for individual cylinders to be speedily performed upon starting of engine. A cylinder identifying means ( 10 ) operating on the basis of a crank angle signal (SGT) and a cam signal (SGC) includes a pulse signal number storage means ( 12 ) for dividing an ignition control period of each cylinder into plural subperiods for counting for storage signal numbers of specific pulses generated over plural subperiods, and a subperiod discriminating means ( 14 ) for determining discriminatively a sequential order of the plural subperiods on the basis of combinations of the numbers of the specific pulses generated during the plural subperiods. The combinations of the numbers of specific pulses generated during the plural subperiods differ one another correspondingly to the plural subperiods independently from the start points thereof. The cylinder identifying means ( 10 ) identifies the individual cylinders on the basis of results of determination made by the subperiod discriminating means ( 14 ) independently of positional relationships between the storage start points and the subperiods.

BACKGROUND OF THE INVENTION

[0001] This application is based on Application No. 2000-317930, filedin Japan on October 18, 2000, the contents of which are herebyincorporated by reference.

[0002] The present invention generally relates to a cylinder identifyingsystem for an internal combustion engine mounted on an automobile or amotor vehicle. More particularly, the present invention is concernedwith a cylinder identifying system for an internal combustion enginewhich system is designed for identifying discriminatively individualcylinders of the internal combustion engine within a short time uponstarting of operation of the engine to thereby allow a fuel injectioncontrol and an ignition control for the engine to be speedily carriedout on a cylinder-by-cylinder basis.

DESCRIPTION OF RELATED ART

[0003] As the hitherto known or conventional cylinder identifying systemof the sort mentioned above, there can be mentioned the one which isdisclosed, for example, in Japanese Unexamined Patent ApplicationPublication No. 146992/1994 (JP-A-6-146992). In the cylinder identifyingsystem described in this publication, a crank angle pulse signalgenerated in synchronism with rotation of a crank shaft of the internalcombustion engine and a cam pulse signal generated in synchronism withrotation of a cam shaft which is operatively coupled to the crank shaftand rotated at a speed ratio of ½ relative to that of the crank shaftare employed for detecting the angle of rotation or angular position ofthe crank shaft on the basis of which engine operation controls such asa fuel injection control, an ignition control, etc. are performed forthe individual cylinders of the engine.

[0004] For generating the crank angle pulse signal, a crank angle sensoris provided which is constituted by a ring gear (or toothed wheel)mounted in a coaxial relation with the crank shaft and having an outerperiphery formed with projections or teeth and an electromagnetic pickupdevice disposed in opposition to the outer periphery of the ring gearfor generating pulses in response to the individual projections orteeth, respectively. The crank angle pulse signal is derived from theoutput signal of the electromagnetic pickup device and includessequentially a series of pulse trains, wherein each pulse traincorresponds to a predetermined angle of rotation of the crank shaft or apredetermined angular range delimited by a reference position.

[0005] On the other hand, the pulse generator for generating the campulse signal is so arranged that the numbers of pulses contained in thecam pulse signals, respectively, differ from one another for the crankangle pulse signals SGT generated successively each over a predeterminedcrank angle range corresponding to given one of the engine cylinders.Thus, on the basis of combination of the numbers of pulses contained inthe cam pulse signals generated within a preceding range (during apreceding period, to say in another way) and within a current range(during a current period), it is certainly possible to identify theindividual cylinder sets as well as particular or specific position(s)in the crank angle pulse signal.

[0006] However, in the conventional cylinder identifying system for theinternal combustion engine, the combinations of the pulse numbersgenerated at the specific positions are limited to three values, i.e.,“0”, “1” and “2”. Accordingly, in the case of a six-cylinder engine, itis impossible to identify discriminatively any given cylinder on thebasis of only the combination of the numbers of pulses generated duringtwo periods (or over two ranges), respectively.

[0007] Further, since the specific position and the cylinders aredetermined discriminatively on the basis of the combination of thenumbers of pulses generated during the preceding period and the currentperiod, respectively, the cylinder identification is rendered impossiblein the case where the end point of the current period does not coincidewith the specific position.

[0008] By way of example, in the case of the four-cylinder engine, therange of crank angles corresponding or equivalent to one period is setto be 90° CA (i.e., 90 degrees in terms of the crank angle or CA inshort). Consequently, the cylinder identification processing can becompleted within a period corresponding to rotation of the engine for180° CA at the shortest although it depends on the crank angle at whichthe engine was stopped in the preceding operation. However, there willarise such situation that the cylinder identification can not becompleted until the engine has rotated over 360° CA at maximum, which ofcourse depends on the crank angle at which the engine was stopped in thepreceding operation. In the latter case, starting of the engineoperation from the stopped state requires a lot of time, needless tosay.

[0009] Another cylinder identifying system for the internal combustionengine is disclosed, for example, in Japanese Unexamined PatentApplication Publication No. 311146/1999 (JP-A-11-311146). In this knowncylinder identifying system, a crank angle pulse signal (POS) includingpulse trains each having a duration or a period which corresponds to apredetermined crank angle range (10° CA) and having a reference positionwhich corresponds to a tooth absent or dropout location in an outerperipheral projection or tooth array of a ring gear, an angle referencesignal (REF) indicating an angle reference differing from the referenceposition mentioned above, and a cam pulse signal (CAM).

[0010] In this cylinder identifying system known heretofore, the campulse signal generating unit is so arranged that the numbers of pulsesgenerated during successive subperiods, respectively, which are definedby dividing a corresponding crank angle period for each engine cylinderdiffer from each other.

[0011] In the system mentioned above, an electronic control unit whichmay be constituted by a microcomputer or the like is so designed as torespond to detection of the angle reference signal REF to thereby dividea range or period defined between a detected start point (leading edge)and an end point (trailing edge) of the angle reference signal REF intoa plurality of subperiods (e.g. two subperiods).

[0012] The durations of the subperiods can be measured with the crankangle pulse signal POS. On the other hand, an array of projections orteeth formed on and along the outer periphery of a rotatable platemounted coaxially with the cam shaft is previously so arranged that thecam pulse signals CAM generated during the subperiods, respectively,differ from each other in respect to the pulse number.

[0013] More specifically, the numbers of pulses of the cam pulse signalsCAM generated during the subperiods are previously set to two differentvalues (e.g. “1” and “0”), respectively, wherein the cylinderidentification can be realized on the basis of combination of thenumbers of the cam pulses generated during the subperiods each extendingfrom a given angle reference signal REF to a succeeding angle referencesignal REF.

[0014] Also in this case, a period extending between the angle referencesignals REF is divided into a plurality of subperiods after detection ofthe angle reference signals REF and then the cylinder identification iscarried out on the basis of combination of the numbers of pulsesgenerated during the plural subperiods, respectively. Thus, the cylinderidentification can be started only after the generation of the anglereference signals REF.

[0015] Such being the circumstances, also in the cylinder identifyingsystem disclosed in Japanese Unexamined Patent Application PublicationNo. 311146/1999, one period which corresponds to revolution of theengine for 180° CA is required for completing the cylinderidentification processing at the shortest although it depends on thecrank angle at which the engine was stopped in the preceding operationthereof, similarly to the case of the cylinder identifying systemdisclosed in Japanese Unexamined Patent Application Publication No.146992/1994. In the worst case, the cylinder identification can not becompleted until the engine has been rotated over 360° CA, which means,needless to say, that a lot of delay time will be involved for startingthe engine operation from the stationary state.

[0016] Further, since the numbers of the pulses generated during thesubperiods, respectively, are set at different values “0” and “1”, theremay arise such situation in the case of the four-cylinder engine thatthe numbers of pulses generated in both the preceding and succeedingsubperiods are “0” and “0”, respectively. In this conjunction, it isnoted that similar situation will take place upon occurrence of a faultsuch as wire breakage. In that case, no cam pulse signal is generated.In other words, distinction from the state in which no cam pulse signalis generated due to a fault is rendered impossible, incurring thus aproblem in respect to the fail-safe function.

[0017] As can now be appreciated from the foregoing description, in theconventional cylinder identifying system disclosed, for example, inJapanese Unexamined Patent Application Publication No. 146992/1994, thespecific or particular position is determined on the basis of thecombination of the numbers of pulses of the cam pulse signal generatedduring predetermined time durations or periods. However, since thenumber of the combinations of the pulse numbers generated at thespecific positions is smaller than the number of the cylinders, it isimpossible to identify any given specific cylinder on the basis of onlythe combination of the numbers of the pulses generated during twodiscrete periods in the case of a six-cylinder internal combustionengine, giving rise to a problem.

[0018] Further, in case the end point of the current period does notcoincide with the specific position, it is impossible to perform thecylinder identification on the basis of the combination of the numbersof the generated pulses of the cam pulse signal. As a consequence, thecylinder identification processing can not be completed until the enginehas rotated for 360° CA at maximum although it depends on the crankangle at which the engine was stopped in the preceding operation,incurring thus a problem that a remarkable time delay will be involvedfor starting again the engine operation.

[0019] On the other hand, in the case of the cylinder identifying systemdisclosed in Japanese Unexamined Patent Application Publication No.311146/1999, the cylinder identification is performed on the basis ofcombination of the numbers of pulses of the cam pulse signal CAMgenerated during a plurality of subperiods defined by dividingcorrespondingly the period of the angle reference signal REF, and thusthe cylinder identification processing is started after generation ofthe angle reference signal REF. Consequently, there also arises theproblem that the cylinder identification processing can not be completeduntil the engine has rotated 360° CA at maximum although it depends onthe crank angle at which the engine was stopped in the precedingoperation, as a result of which a lot of time is taken for startingagain the engine operation.

[0020] Furthermore, since the numbers of pulses generated during thesubperiods, respectively, are set to two different values, such problemis incurred that when the number of pulses generated in both thesubperiods of the cylinder identification period are “0” and “0”,distinction from the state where no cam pulse signal is outputted due tooccurrence of a fault such as wire breakage is rendered impossible,giving rise to a problem in respect to the fail-safe performance.

SUMMARY OF THE INVENTION

[0021] In the light of the state of the art described above, it is anobject of the present invention to provide a cylinder identifying systemfor an internal combustion engine which system is capable of performingthe cylinder identification within a smaller angular range of enginerotation and hence within a shortened time to thereby enable the fuelinjection control and the ignition control for each engine cylinder tobe speedily carried out upon engine starting operation.

[0022] In view of the above and other objects which will become apparentas the description proceeds, there is provided according to a generalaspect of the present invention a cylinder identifying system for aninternal combustion engine, which system includes a crank angle signaldetecting means for generating a crank angle pulse signal composed ofpulse trains each containing a reference position in synchronism withrotation of a crank shaft of the internal combustion engine, a cam shaftrotating at a speed corresponding to one half of that of the crankshaft, a cam signal detecting means for generating a cam pulse signalincluding specific pulses identifying individual cylinders,respectively, of the internal combustion engine in synchronism withrotation of the cam shaft, and a cylinder identifying means foridentifying the individual cylinders, respectively, of the internalcombustion engine on the basis of the crank angle pulse signal and thecam pulse signal. In the cylinder identifying system mentioned above,the cylinder identifying means is comprised of a pulse signal numberstorage means for dividing an ignition control period for each of theindividual cylinders into a plurality of subperiods for thereby countingfor storage signal numbers of the specific pulses generated during theplural subperiods, respectively, and a subperiod discriminating meansfor determining discriminatively a sequential order of the pluralsubperiods on the basis of combinations of the signal numbers of thespecific pulses generated during the plural subperiods, respectively.The combinations of the signal numbers of the specific pulses generatedduring the plural subperiods, respectively, differ from one to anothercorrespondingly to the plural subperiods in dependence on start pointsof the plural subperiods, respectively. The cylinder identifying meansis so designed as to identify the individual cylinders on the basis ofresults of the discriminative determination of the subperiods performedby the subperiod discriminating means independently of the start pointsof the plural subperiods.

[0023] By virtue of the arrangement described above, there is providedfor an internal combustion engine the cylinder identifying systemcapable of performing the cylinder identification within a smallerangular range of engine rotation and hence within a shortened time forthereby allowing the fuel injection control and the ignition control foreach engine cylinder to be speedily carried out upon engine startingoperation.

[0024] In a preferred mode for carrying out the invention, the pulsesignal number storage means may be so designed as to count for storagethe signal number of the cam pulse signal and the number of pulses ofthe crank angle pulse signal, respectively, from the start of operationof the internal combustion engine. The cylinder identifying means may beconstituted by a pulse signal sequential order storage means for storingtherein temporal relations between the pulse trains of the crank anglepulse signal and the specific pulses of the cam pulse signal, and areference position detecting means for detecting the reference positionfrom the crank angle pulse signal, wherein when it is decided that thecrank angle pulse signal has been detected since a start point of apreceding subperiod at the latest on the basis of the number of pulsesof the crank angle pulse signal which have been stored up to thereference position, the cylinder identifying means identifies theindividual cylinders on the basis of the signal number of the cam pulsesignal(s) generated during the preceding subperiod.

[0025] In another preferred mode for carrying out the invention, thecylinder identifying means may be so arranged that when it is decidedafter detection of the reference position that the crank angle pulsesignal has been detected since the start point of the current subperiodat the latest on the basis of the pulse number of the crank angle pulsesignal stored up to a time point at which an end point of the currentsubperiod including the reference position is detected, the cylinderidentifying means identifies the individual cylinders on the basis ofthe signal number of the cam pulse signal(s) generated during thecurrent subperiod.

[0026] In yet another mode for carrying out the invention, the cylinderidentifying means may preferably be so implemented that when it isdecided on the basis of the pulse number of the crank angle pulse signalstored up to a subperiod end point of the plural subperiods that thecrank angle pulse signal has been detected since the start point of thepreceding subperiod at the latest, the cylinder identifying means thenidentifies the individual cylinders on the basis of combination of thesignal number of the cam pulse signal(s) generated during the precedingsubperiod and the signal number of the cam pulse signal(s) generatedduring the current subperiod.

[0027] Owing to the arrangements of the cylinder identifying systemdescribed above, the fuel injection control and the ignition control canbe speedily carried out for the individual engine cylinders upon enginestarting operation.

[0028] In still another mode for carrying out the present invention,such arrangement should preferably by adopted that the combinations ofthe signal numbers of the cam pulse signals generated during the pluralsubperiods includes no combination of only “0s” which indicates absenceof output.

[0029] With the arrangement described above, there can be realized thecylinder identifying system which can ensure a fail-safe functiondescribed later on.

[0030] In a further mode for carrying out the present invention which isapplied to a four-cylinder internal combustion engine in which theignition control period for each of the cylinders is so set as tocorrespond to a crank angle of 180°, the plural subperiods shouldpreferably be comprised of a first subperiod and a second subperiod,wherein numbers of the specific pulses contained in the cam pulse signalgenerated during the first subperiod and the second subperiod,respectively, should be “1” and “0”, “2” and “1”, “0” and “2” and “0”and “1”, respectively, in the order in which the cylinders are to becontrolled.

[0031] In a yet further mode for carrying out the present inventionapplied to a six-cylinder internal combustion engine in which theignition control period for each of the cylinders is so set as tocorrespond to a crank angle of 120°, the plural subperiods shouldpreferably be comprised of a first subperiod and a second subperiod,wherein numbers of the specific pulses contained in the cam pulse signalgenerated during the first subperiod and the second subperiod,respectively, should be “1” and “0”, “2” and “0”, “1” and “2”, “0” and“2”, “1” and “1” and “0” and “1”, respectively, in the order in whichthe cylinders are controlled.

[0032] In a still further mode for carrying out the present inventionapplied to a three-cylinder internal combustion engine in which theignition control period for each of the cylinders is so set as tocorrespond to a crank angle of 240°, the plural subperiods shouldpreferably include a first subperiod and a second subperiod, whereinnumbers of the specific pulses contained in the cam pulse signalgenerated during the first subperiod and the second subperiod,respectively, should be “1” and “0”, “2” and “0”, “1” and “2”, “0” and“2”, “1” and “1” and “0” and “1”, respectively, in the order in whichthe cylinders are controlled.

[0033] Owing to the features described above, there can be realized thecylinder identifying system which can ensure the fail-safe functionwhile enabling the fuel injection control and the ignition control foreach engine cylinder to be speedily carried out upon engine startingoperation.

[0034] In a further mode for carrying out the invention, the crank anglepulse signal should preferably be comprised of pulse trains each of aperiod corresponding to a crank angle of 10°, wherein the referenceposition included in the crank angle pulse signal should be set at acrank angle of 350 from the top dead center on a cylinder-by-cylinderbasis.

[0035] With the arrangement described above, the fuel injection controland the ignition control can speedily be carried out for each of theengine cylinders while ensuring enhanced controllability and highcontrol accuracy.

[0036] The above and other objects, features and attendant advantages ofthe present invention will more easily be understood by reading thefollowing description of the preferred embodiments thereof taken, onlyby way of example, in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In the course of the description which follows, reference is madeto the drawings, in which:

[0038]FIG. 1 is a functional block diagram showing generally andschematically a cylinder identifying system for an internal combustionengine according to a first embodiment of the present invention;

[0039]FIG. 2 is a timing chart showing signal patterns of a crank anglepulse signal and a cam pulse signal, respectively, in an internalcombustion engine including four cylinders according to the firstembodiment of the present invention;

[0040]FIG. 3 is a timing chart for illustrating cylinder identifyingoperation performed in the cylinder identifying system according to thefirst embodiment of the present invention;

[0041]FIG. 4 is a view for illustrating a cylinder identification tablebased on subperiods (a) and (b) which is referenced in conjunction withthe signal detection pattern illustrated in FIG. 3;

[0042]FIG. 5 is a timing chart for illustrating a second example of thecylinder identifying operation carried out in the cylinder identifyingsystem according to the first embodiment of the present invention;

[0043]FIG. 6 is a view showing a cylinder identification table based onsubperiods (b) and (a) to be referenced in conjunction with the signaldetection pattern illustrated in FIG. 5;

[0044]FIG. 7 is a timing chart for illustrating a third example of thecylinder identifying operation carried out in the cylinder identifyingsystem according to the first embodiment of the present invention;

[0045]FIG. 8 is a timing chart for illustrating a fourth example of thecylinder identifying operation performed in the cylinder identifyingsystem according to the first embodiment of the present invention;

[0046]FIG. 9 is a view showing a cylinder identification table based ona TDC period to be referenced during an ordinary operation in thecylinder identifying system according to the first embodiment of thepresent invention;

[0047]FIG. 10 is a flow chart for illustrating an interrupt processingroutine executed by a cylinder identifying means in response to a campulse signal in the cylinder identifying system according to the firstembodiment of the present invention;

[0048]FIG. 11 is a flow chart for illustrating an interrupt processingroutine executed by the cylinder identifying means in response to acrank angle pulse signal in the cylinder identifying system according tothe first embodiment of the present invention;

[0049]FIG. 12 is a flow chart for illustrating an interrupt processingroutine executed by the cylinder identifying means in response to acrank angle pulse signal in the cylinder identifying system according tothe first embodiment of the present invention;

[0050]FIG. 13 is a flow chart for illustrating an interrupt processingroutine executed by the cylinder identifying means in response to acrank angle pulse signal in the cylinder identifying system according tothe first embodiment of the present invention;

[0051]FIG. 14 is a flow chart for illustrating an interrupt processingroutine executed by the cylinder identifying means in response to acrank angle pulse signal in the cylinder identifying system according tothe first embodiment of the present invention;

[0052]FIG. 15 is a timing chart showing signal patterns of a crank anglepulse signal and a cam pulse signal generated in an internal combustionengine having six-cylinders according to a second embodiment of thepresent invention;

[0053]FIG. 16 is a timing chart for illustrating, by way of example, acylinder identifying operation carried out by the cylinder identifyingsystem according to the second embodiment of the present invention;

[0054]FIG. 17 is a view showing a cylinder identification table based onsubperiods (a) and (b) to be referenced in conjunction with a signaldetection pattern illustrated in FIG. 16;

[0055]FIG. 18 is a timing chart for illustrating a second example of thecylinder identifying operation carried out by the cylinder identifyingsystem according to the second embodiment of the present invention;

[0056]FIG. 19 is a view showing a cylinder identification table based onsubperiods (b) and (a) to be referenced in conjunction with a signaldetection pattern illustrated in FIG. 18;

[0057]FIG. 20 is a timing chart for illustrating a third example of thecylinder identifying operation carried out by the cylinder identifyingsystem according to the second embodiment of the present invention;

[0058]FIG. 21 is a timing chart for illustrating a fourth example of thecylinder identifying operation performed by the cylinder identifyingsystem according to the second embodiment of the invention;

[0059]FIG. 22 is a view showing a cylinder identification table based ona TDC period for reference during an ordinary operation in the cylinderidentifying system according to the second embodiment of the presentinvention;

[0060]FIG. 23 is a timing chart showing signal patterns of a crank anglepulse signal and a cam pulse signal generated in a three-cylinder engineaccording to a third embodiment of the present invention;

[0061]FIG. 24 is a view showing a cylinder identification table based onsubperiods (a) and (b) as employed in the cylinder identifying systemaccording to the third embodiment of the present invention; and

[0062]FIG. 25 is a view showing a cylinder identification table based onsubperiods (b) and (a) as employed in the cylinder identifying systemaccording to the third embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0063] The present invention will be described in detail in conjunctionwith what is presently considered as preferred or typical embodimentsthereof by reference to the drawings. In the following description, likereference characters designate like or corresponding parts throughoutthe several views.

[0064] Embodiment 1

[0065]FIG. 1 is a functional block diagram showing generally andschematically a cylinder identifying system for an internal combustionengine according to a first embodiment of the present invention.Referring to the figure, an internal combustion engine (also referred tosimply as the engine) includes a crank shaft 1 and a cam shaft 2 whichrotates at a speed corresponding to one half of that of the crank shaft1.

[0066] A crank angle signal detecting means 3 is provided in associationwith the crank shaft 1 so as to rotate in synchronism with the crankshaft 1 for thereby generating a crank angle pulse signal SGT in theform of pulse train each containing a pulse indicative of a referenceposition. On the other hand, provided in association with the cam shaft2 is a cam signal detecting means 4 which rotates synchronously with thecam shaft 2 for generating a cam pulse signal SGC including particularor specific pulses (signals) for identifying individual cylinders,respectively, of the engine.

[0067] A cylinder identifying means 10 which may be constituted by anelectronic control unit is provided for identifying the individualcylinders and determining discriminatively the reference position foreach of the cylinders on the basis of the crank angle pulse signal SGTand the cam pulse signal SGC. To this end, the cylinder identifyingmeans 10 includes a pulse signal sequential order storage means 11 and apulse signal number storage means 12 designed for storing the crankangle pulse signal SGT and the cam pulse signal SGC, a referenceposition detecting means 13 for fetching the crank angle pulse signalSGT, and an subperiod discriminating means 14 for fetching outputsignals of the pulse signal number storage means 12 and the referenceposition detecting means 13, respectively.

[0068] The pulse signal sequential order storage means 11 is designed tostore therein the temporal relation between the pulse trains each havinga duration of 10° in terms of the crank angle (hereinafter referred toas the CA in short) which are contained in the crank angle pulse signalSGT and the specific pulses for the cylinder identification contained inthe cam pulse signal SGC.

[0069] On the other hand, the pulse signal number storage means 12 iscomprised of a crank angle signal storage means for storing the numberof the pulses of the crank angle pulse signal SGT as detected since thestart of the engine operation and a cam signal storage means for storingthe number of signal pulses of the cam pulse signal SGC generated sincethe start of the engine operation and serves for counting for storagethe number of the pulses of the crank angle pulse signal SGT and thesignal pulses of the cam pulse signal SGC, respectively, from the timepoint at which the engine operation is started.

[0070] Further, the pulse signal number storage means 12 is designed todivide the ignition control period for each of the individual cylindersinto a plurality of subperiods for thereby counting for storage thesignal number of the specific pulses generated over the plurality ofsubperiods. In this conjunction, it is presumed, by way of example, thatthe ignition control period is divided into two subperiods (a) and (b)only for the convenience of description, as will hereinafter be madeclear.

[0071] The reference position detecting means 13 is designed to detectthe reference position on the basis of the crank angle pulse signal SGT,while the subperiod discriminating means 14 is designed to decidediscriminatively the sequential order of the plural subperiods, i.e.,whether the subperiods are in the sequential order of the subperiod (a)and then the subperiod (b) or in the order of the subperiod (b) and thenthe subperiod (a), on the basis of combination of the signal numbers ofthe specific pulses generated during the plural subperiods,respectively.

[0072]FIG. 2 is a timing chart showing patterns of the crank angle pulsesignal SGT and the cam pulse signal SGC, respectively, generated in theinternal combustion engine according to the instant embodiment of thepresent invention on the presumption that the internal combustion engineconcerned includes four cylinders, by way of example.

[0073] Referring to FIG. 2, the crank angle pulse signal SGT includes atooth dropout position (pulse absent position) A25° CA (i.e., positionsucceeding to the top dead center (TDC) by 25° in terms of the crankangle, hereinafter denoted simply by “position A25”) for each of theengine cylinders #1 to #4. Parenthetically, in FIG. 2, the crank anglepositions are shown over a range extending from a position B95° CA(i.e., position preceding to the top dead center by 95° in terms of thecrank angle or CA, hereinafter denoted simply by “position B95”)approximately to the position A25 around the center of approximatelyB05° CA (i.e., position preceding to the top dead center by 5° in termsof CA, hereinafter denoted simply by “position B05”) for each of theengine cylinders.

[0074] In more concrete, the crank angle pulse signal SGT is composed ofpulse trains containing pulses generated every 10° CA, wherein the toothdropout position A25 corresponds to the position of a ring gear whereone tooth is dropped or absent. Consequently, the reference positiondetected actually in correspondence to the tooth dropout is the positionsucceeding to the top dead center (TDC) by 35° in terms of crank angle(hereinafter referred to as “position A35”).

[0075] Each of the TDC period (top dead center periods) which extendsover the angular range of 180° CA of the crank angle pulse signal SGT isdivided into plural subperiods (two subperiods in the case of theillustrated example), i.e., the subperiod (a) containing the referenceposition A35 (corresponding to the tooth dropout position) and thesubperiod (b) which does not include the reference position A35.

[0076] On the other hand, the cam pulse signal SGC includes differentnumbers of the specific signal pulses (combinations of “0”, “1”and “2”)in correspondence to the individual cylinders. More specifically, whenthe ignition control period for each of the cylinders is divided into aplurality of subperiods (two subperiods), the cam pulse signal SGC is soset that combinations of the numbers of the specific signal pulsesgenerated in each of the subperiod (a) and the subperiod (b) differ incorrespondence to the plural subperiods in dependence on the startpoints thereof, respectively. Incidentally, when the storage of thespecific pulses is started from an intermediate time point of thesubperiod, the data acquired during a period extending from the storagestart point to the start point of the first succeeding subperiod is notused for the cylinder identification.

[0077] In this manner, the cylinder identifying means 10 is so designedas to be capable of identifying or discerning discriminatively theindividual cylinders on the basis of the result of determination of thesubperiod discriminating means 14 independently of the positionalrelationships between the storage starting point of the pulse signalnumber storage means 12 and the plural subperiods (a) and (b).

[0078] More specifically, the cylinder identifying means 10 identifiesdiscriminatively the cylinders on the basis of the number of pulses ofthe crank angle pulse signal SGT which have been stored until thereference position A35 located adjacent to the tooth dropout positionA25 is detected.

[0079] In other words, when it is decided that the crank angle pulsesignal SGT has been detected since the start point of the preceding oneof the plural subperiods at the latest, the cylinder identifying means10 identifies the individual cylinders on the basis of the number ofpulses of the cam pulse signal SGC generated during the precedingsubperiod.

[0080] On the other hand, when it is decided that the crank angle pulsesignal SGT has been detected from the start point of the currentsubperiod at the latest on the basis of the number of pulses of thecrank angle pulse signal SGT stored up to the time point at which theend point of the current subperiod including the reference position A35among the plural subperiods is detected, the cylinder identifying means10 identifies the individual cylinders on the basis of the signal numberof the cam pulse signal SGC generated during the current subperiod.

[0081] Furthermore, when it is decided on the basis of the number ofpulses of the crank angle pulse signal SGT stored till the detection ofthe end point of the plural subperiods that the crank angle pulse signalSGT has been detected since the start of the preceding subperiod at thelatest, the cylinder identifying means 10 identifies the individualcylinders on the basis of the combination of the signal number of thecam pulse signal SGC generated during the preceding subperiods and thesignal number of the cam pulse signal SGC generated during the currentsubperiod.

[0082] At this juncture, it should be mentioned that the combination ofthe signal numbers of the cam pulse signal SGC generated during theplural subperiods (a) and (b) contains no combination of “0” and “0”indicating the absence of output. In other words, at least one of thesignal numbers generated during the subperiods (a) and (b) is “1” or“2”.

[0083] It should also be added that the cam pulse signal SGC is sogenerated that a predetermined number of pulse signals make appearanceduring subperiod in consideration of the phase difference between thecrank angle pulse signal SGT and the cam pulse signal SGC.

[0084] Now, referring to FIG. 2, it is presumed, by way of example, thatthe top dead center (TDC) period of each cylinder is so set as to extendfrom a position B05 close to the top dead center (TDC) of a givencylinder to a position B05 close to the top dead center (TDC) of asucceeding cylinder. Incidentally, the position B05 will also bereferred to as the top dead center only for convenience of thedescription, because the position B05 is located very closely to the topdead center.

[0085] In the subperiods (a) and (b) defined by dividing by two the TDCperiod (also referred to as the ignition control period) extending fromthe top dead center (B05) of the cylinder #2 to the top dead center(B05) of the succeeding cylinder #1, the pulse numbers of the cam pulsesignal SGC generated during these subperiods (a) and (b) are “1” and“0”, respectively.

[0086] Similarly, the number of pulses generated during the subperiods(a) and (b) defined, respectively, by dividing by two the TDC periodextending from the top dead center (B05) of the cylinder #1 to that(B05) of the cylinder #3 are “2” and “1”, respectively, while the numberof the pulses generated during the subperiods (a) and (b) defined,respectively, by dividing by two the TDC period extending from the topdead center (B05) of the cylinder #3 to that (B05) of the cylinder #4are “0” and “2”, respectively, and the number of pulses generated duringthe subperiods (a) and (b) defined, respectively, by dividing by two theTDC period extending from the top dead center (B05) of the cylinder #4to that (B05) of the cylinder #2 are “0” and “1”, respectively.

[0087] In the following, description will be made of the cylinderidentifying operation carried out by the cylinder identifying systemaccording to the instant embodiment of the invention shown in FIG. 1 byreferring to FIGS. 2 to 8. In the first place, description will bedirected to the typical cylinder identifying operation by referring toFIGS. 2 to 4.

[0088]FIG. 3 is a timing chart for illustrating operation of thecylinder identifying means 10 incorporated in the cylinder identifyingsystem shown in FIG. 1. More specifically, there is illustrated a pulsesignal detection pattern in the case where detection of the crank anglepulse signal SGT and the cam pulse signal SGC is started from a positionimmediately before the position B05 of the cylinder #1 (the start pointof the subperiods (a)) upon starting of the engine operation.

[0089]FIG. 4 is a view for illustrating a cylinder identification tablewhich is referenced in conjunction with the pulse signal detectionpattern illustrated in FIG. 3. This cylinder identification table isincorporated or stored in the subperiod discriminating means 14.

[0090] Referring to FIG. 3, when the signal detection is started from aposition (B05) immediately before the top dead center of the cylinder #1upon starting of the engine operation, the numbers of pulses of thecrank angle pulse signal SGT and the cam pulse signal SGC, respectively,which have been detected since the time point corresponding to theposition B05, are firstly counted to be stored in the pulse signalnumber storage means 12.

[0091] Subsequently, the reference position detecting means 13incorporated in the cylinder identifying means 10 arithmeticallydetermines the preceding period Tsgt(n−1) and the current period Tsgt(n)of the crank angle pulse signal SGT, respectively, whereon the ratio ofthe period Tsgt(n) to the period Tsgt(n−1) is arithmetically determinedas a period ratio TR(n) in advance in accordance with the followingexpression:

TR(n)=Tsgt(n)/Tsgt(n−1)  (1)

[0092] In succession, the reference position detecting means 13 makesdecision as to whether or not the period ratio TR(n) of the crank anglepulse signal SGT is equal to or greater than a predetermined value Kr.When it is decided that TR(n)≧Kr, the reference position A35 isdetected.

[0093] In this conjunction, the predetermined value Kr mentioned aboveis so selected in consideration of variation of rotation of the enginethat the reference position A35 (corresponding to the dropout toothposition) can be determined when the period ratio TR(n) is about twiceas large as the ordinary value.

[0094] At the time point when the reference position A35 is detected,the cylinder identifying means 10 is not in the position to identify thecylinder yet. However, it is possible to discriminatively determine thatthe current subperiod (i.e., the subperiod currently concerned) is thesubperiod (a).

[0095] Furthermore, when it is found by referencing the data stored inthe pulse signal number storage means 12 that the pulse number of thecrank angle pulse signal SGT detected during the period extending fromthe start of detection of the signal SGT to the detection of thereference position A35 is equal to or greater than “4”, it can then bedecided that the detection has been started from the start point B05 ofthe subperiod (a) at the latest, which means that the number of pulsesof the crank angle pulse signal SGT at the time point corresponding tothe position B05 can be confirmed.

[0096] Now, the subperiod discriminating means 14 incorporated in thecylinder identifying means 10 makes reference to the data stored in thepulse signal number storage means 12 for determining the end position orpoint B95 of the subperiod (a). In this case, the detected pulse numberof the crank angle pulse signal SGT indicates the number of pulses ofthe crank angle pulse signal SGT detected during the period extendingfrom the start of the detection to the current time point.

[0097] When the number of pulses of the crank angle pulse signal SGT asdetected since the detection time point corresponding to the positionB05 is “9”, this means that the current time point corresponds to theend point or position B95 of the subperiod (a). Accordingly, the numberof pulses of the cam pulse signal SGC as detected up to this time point(i.e., during the subperiod (a)) is checked. In the case of the exampleillustrated in FIG. 3, the number of pulses of the cam pulse signal SGCgenerated during the subperiod (a) is “2”.

[0098] Subsequently, the subperiod discriminating means 14 incorporatedin the cylinder identifying means 10 refers to the data stored in thepulse signal number storage means 12 for detecting the end point orposition B05 of the subperiod (b) which succeeds to the subperiod (a)mentioned above.

[0099] On the other hand, when the number of pulses of the crank anglepulse signal SGT detected since the start point B95 of the subperiod (b)up to the current time point is “9”, this means that the current timepoint corresponds to the end point or position B05 of the subperiod (b).Accordingly, the number of pulses of the cam pulse signal SGC asdetected up to this time point (i.e., during the subperiod (b)) ischecked. In the case of the example illustrated in FIG. 3, the number ofpulses of the cam pulse signal SGC generated during the subperiod (b) is“1”.

[0100] Thus, the numbers of pulses of the cam pulse signal SGC generatedduring the subperiods (a) and (b) are “2” and “1”, respectively.Accordingly, by referencing the cylinder identification table shown inFIG. 4 by the cylinder identifying means 10, it can be found that thecurrent crank angle position detected latest is the top dead center(B05) of the cylinder #3.

[0101] In the case where detection of the crank angle pulse signal SGTis started from a time point immediately preceding to the start point(B05) of the subperiod (a) by starting the engine operation at that timepoint, the cylinder identification processing will be completed within atime period corresponding to the crank angle range of about 180° CA, ascan be seen from FIG. 3.

[0102] Furthermore, as can be seen in FIGS. 2 to 4, when the number ofpulses of the cam pulse signal SGC generated during the subperiod (a) is“1” or “2”, it can straight-forwardly be decided that the current crankangle position coincides with the position B95 of the cylinder #1 or thecylinder #3 on the basis of only the number of pulses generated duringthe subperiod (a) already at the detection time point corresponding tothe position B95 without need for referencing the number of pulsesgenerated during the succeeding subperiod (b).

[0103] In this case, the range of the crank angle corresponding to thetime lapse from the start of detection of the crank angle pulse signalSGT upon starting of the engine to the cylinder identification isapproximately 90° CA.

[0104] Next, referring to FIGS. 5 and 6 together with FIG. 2,description will be directed to another typical or exemplary operations.FIG. 5 is a timing chart for illustrating operation when the signaldetection is started from a time point immediately preceding to theposition B95 of the cylinder #1 (i.e., at the start point of thesubperiod (b)) upon starting of the engine operation, and FIG. 6 is aview for illustrating a cylinder identification table which isreferenced in conjunction with the pulse signal detection patternillustrated in FIG. 5.

[0105] Referring to FIG. 5, when the signal detection is started from aposition immediately preceding to the position B95 of the cylinder #1,the pulse numbers of the crank angle pulse signal SGT and the cam pulsesignal SGC, respectively, which have been detected from the time pointcorresponding to the position B95 are firstly counted to be stored inthe pulse signal number storage means 12.

[0106] In that case, the reference position A35 is not detected duringthe subperiod (b) whose start point is the position B95. Accordingly,even at the time point when the start point B05 of the succeedingsubperiod (a) has been reached, it is impossible to determine definitelythe absolute value of the crank angle position.

[0107] Subsequently, at the time point when the reference position A35is detected, the subperiod discriminating means 14 determines theabsolute value of the crank angle A35 for thereby discriminatingdefinitely the subperiods of the individual cylinders on the basis ofthe number of pulses contained in the crank angle pulse signal SGTdetected since the time point when the engine was started.

[0108] More specifically, when the number of detected pulses of thecrank angle pulse signal SGT is “13” or more, it can be decided that thepulse detection has been started from a time point corresponding to orpreceding to the start point B95 of the subperiod (b), and thus, thestart point B95 can discriminatively be determined.

[0109] In this manner, when it can be verified that the crank anglepulse signal SGT has been detected over the time span from the startpoint B95 of the subperiod (b) up to the end point B05 thereof, i.e.,when the crank angle pulse signal SGT has been detected throughout thesubperiod (b) wholly, the cylinder identifying means 10 can check thenumber of pulses contained in the cam pulse signal SGC detected duringthe subperiod (b)). Incidentally, in the case of the example illustratedin FIG. 5, the number of pulses generated during the subperiod (b) is“0”.

[0110] In succession, the subperiod discriminating means 14 incorporatedin the cylinder identifying means 10 detects the position B95 of thecylinder #3 (the end point of the subperiod (a)) and confirms or detectsthat the number of pulses contained in the cam pulse signal SGCgenerated during the subperiod (a) is “2”.

[0111] As is apparent from the above, the numbers of pulses generatedduring the individual subperiods (b) and (a) are “0” and “2”,respectively. Accordingly, by referencing the cylinder identificationtable shown in FIG. 6, the cylinder identifying means 10 can determinethat the current crank angle position is the position B95 of thecylinder #3 (the end point of the subperiod (a)).

[0112] As is illustrated in FIG. 5, in the case where detection of thecrank angle pulse signal SGT is started with from a time pointimmediately preceding to the start point B95 of the subperiod (b) bystarting the engine operation from that time point, the cylinderidentification can be completed within a time span corresponding to thecrank angle range of about 180° CA.

[0113] Furthermore, as can be seen in FIGS. 2 to 6, when the number ofpulses of the cam pulse signal SGC generated during the subperiod (b) is“2”, it can straightforwardly be decided that the current crank angleposition is the position B05 of the cylinder #4 on the basis of only thenumber of pulses generated during the subperiod (b) already at the timepoint corresponding to the position B05 without need for referencing thedata concerning the number of pulses generated during the succeedingsubperiod (a).

[0114] In this case, the range of the crank angle corresponding to thetime lapse from the start of the pulse signal detection validated uponstarting of the engine operation to the cylinder identification is about130° CA.

[0115] Next, referring to FIG. 7, description will be directed to theoperation in the case where a maximum range of the crank angle isinvolved for the cylinder identification. FIG. 7 is a timing chart forillustrating operation when the signal detection is started from a timepoint or position immediately succeeding to the position B95 of thecylinder #1 (i.e., the start point of the subperiod (b)) upon startingof engine operation.

[0116] In this case, the signal detection start position lies in thevicinity of the position B85° CA immediately succeeding to the positionB95. Accordingly, the detected number of pulses of the crank angle pulsesignal SGT at the time point when the reference position A35(corresponding to the dropout tooth position) was detected is “12”.

[0117] Thus, the reference position detecting means 13 candiscriminatively determine the reference position A35 in terms of theabsolute angle value.

[0118] However, since detection of the crank angle pulse signal SGT isnot started from the start point B95 of the subperiod (b), the detectedpulse number “12” of the crank angle pulse signal SGT is not sufficientfor the subperiod discriminating means 14 to get information concerningthe number of pulses of the cam pulse signal SGC generated during thesubperiod (b) firstly subjected to the pulse detection.

[0119] Subsequently, at the time point when the end point B95 of thesubperiod (a) is detected on the basis of the number of pulses “6” ofthe crank angle pulse signal SGT detected since the time pointcorresponding to the reference position A35, the subperioddiscriminating means 14 confirms that the number of pulses of the campulse signal SGC generated during the subperiod (a) is “2”.

[0120] In succession, at the time point when the end point of thesubperiod (b) (i.e., position B05 of the cylinder #3) is detected on thebasis of the number of pulses “9” of the crank angle pulse signal SGTdetected since the time point corresponding to the position B95 of thecylinder #3, the subperiod discriminating means 14 confirms that thenumber of pulses of the cam pulse signal SGC generated during thesubperiod (b) is “1”.

[0121] As is apparent from the above, the numbers of pulses generatedduring the individual subperiods (a) and (b) are “2” and “1”,respectively. Accordingly, by referencing the cylinder identificationtable shown in FIG. 4, the cylinder identifying means 10 can determinethat the current crank angle position coincides with the position B05 ofthe cylinder #3.

[0122] As can be seen in FIG. 7, in the case where detection of thepulse signal is started from a time point immediately succeeding to thestart of the subperiod (b) validated upon starting of the engineoperation, the cylinder identification will be completed within a timeperiod corresponding to the crank angle range of about 270° CA.

[0123] Also in this case, when the number of pulses of the cam pulsesignal SGC generated during the subperiod (a) is “2” or “1”, thecylinder identification can straightforwardly be performed only on thebasis of the number of the pulses generated during the subperiod (a).Namely, it can be determined that the time required for completing thecylinder identification processing is equivalent to the crank angle ofabout 180° CA.

[0124] Next, referring to FIG. 8, description will be directed toanother example of operation in which a maximum range of the crank angleis required for the cylinder identification. FIG. 8 is a timing chartfor illustrating operation when the signal detection is started from atime point or position immediately succeeding to the position B05 of thecylinder #2 (i.e., the start point of the subperiod (a)) upon startingof the engine operation.

[0125] Referring to FIG. 8, the position for starting the detection ofthe crank angle pulse signal SGT is the position A05° CA immediatelysucceeding to the position B05 of the cylinder #2.

[0126] Thus, at the time point when the absolute value A35 of the crankangle (corresponding to the dropout tooth position) is detected, it canbe determined that the crank angle pulse signal SGT has not beendetected since the start point (B05) of the subperiod (a) because thenumber of pulses of the crank angle pulse signal SGT detected since thestart of engine operation is “3”.

[0127] Accordingly, at the time point when the position B95 of thecylinder #1 (end point of the subperiod (a)) is detected, the number ofpulses of the cam pulse signal SGC generated during the subperiod (a) isnot clear. Thus, the subperiod discriminating means 14 is not in theposition to discriminatively determine the number of pulses generated.

[0128] In succession, at the time point when the position B05 of thecylinder #1 (i.e., the end point of the subperiod (b)) is detected onthe basis of the number of pulses “9” of the crank angle pulse signalSGT detected since the time point corresponding to the position B95 ofthe cylinder #1, the subperiod discriminating means 14 can verify thatthe number of pulses of the cam pulse signal SGC generated during thesubperiod (b) is “0”.

[0129] Next, the reference position A35 of the cylinder #1 is detectedand then the position B95 of the succeeding cylinder #3 (i.e., the endpoint of the subperiod (a)) is detected on the basis of the number ofpulses “6”, of the crank angle pulse signal SGT detected since the timepoint corresponding to the position A35 of the cylinder #1. Thus, thesubperiod discriminating means 14 can confirm that the number of pulsesof the cam pulse signal SGC generated during the subperiod (a) is “2”.

[0130] As is apparent from the above, the numbers of pulses generatedduring the subperiods (b) and (a) are “0” and “2”, respectively.Accordingly, by referencing the cylinder identification table shown inFIG. 6, the cylinder identifying means 10 determines that the currentcrank angle position coincides with the position B95 of the cylinder #3.

[0131] Referring to FIG. 8, in the case where detection of the pulsesignal is started from a time point immediately succeeding to the startpoint of the subperiod (a) upon starting of the engine operation, thecylinder identification will be completed within a time spancorresponding to the crank angle range of about 270° CA.

[0132] Further, when the number of pulses of the cam pulse signal SGCgenerated during the subperiod (b) checked firstly is “2”, as describedabove, the cylinder identification processing is immediately terminated.Thus, the time required for completing the cylinder identificationprocessing is equivalent to the crank angle of about 180° CA.

[0133] As is apparent from the foregoing, in any one of the casesdescribed by reference to FIG. 3, FIG. 5, FIG. 7 and FIG. 8,respectively, the cylinder identifying operation or processing in theengine operation starting state can be completed during a shorter period(i.e., within a smaller range of the crank angle) when compared with theconventional cylinder identifying system.

[0134] By the way, in the ordinary operation which succeeds to thecylinder identification, the cylinder identification processing canequally be carried out continuously on the basis of the combinations ofthe numbers of pulses of the cam pulse signal SGC generated during thecurrent subperiod and the preceding subperiod, respectively, byreference to the table shown in FIG. 4 or FIG. 6 at the end points ofthe subperiods (a) and (b), respectively.

[0135] In this conjunction, it should further be mentioned that in orderto simplify and speed up the cylinder identification processing in theordinary operation, the cylinder identification procedure may becontinued on the basis of the number of pulses of the cam pulse signalSGC generated during both the subperiods (a) and (b) (i.e., during theTD period intervening between the positions B05 of the individualcylinders without resorting to the division of the TDC period into thesubperiods (a) and (b). FIG. 9 is a view showing a cylinderidentification table prepared as based on the number of pulses of thecam pulse signal SGC generated during the TDC period on acylinder-by-cylinder basis. In this case, the cylinder identifying means10 is so designed as to check the sum of the numbers of pulses generatedduring the subperiods (a) and (b) to thereby identify the individualcylinders on the basis of the combinations of the numbers of the pulsesgenerated in the preceding TDC period and the current TDC period bymaking reference to the cylinder identification table shown in FIG. 9.

[0136] Next, referring to flow charts shown in FIGS. 10 to 14 togetherwith FIGS. 2 to 9, the processing operations carried out by the cylinderidentifying means 10 of the cylinder identifying system according to thefirst embodiment of the present invention shown in FIG. 1 will beelucidated in more concrete.

[0137] FIGS. 10 to 14 show flow charts for illustrating the cylinderidentification processing executed upon starting of operation of afour-cylinder internal combustion engine, wherein FIG. 10 shows aninterrupt processing routine (also referred to as the interrupt handlingroutine) activated in response to the cam pulse signal SGC, and FIGS. 11to 14 show interrupt processing routines, respectively, which are alsoactivated in response to the crank angle pulse signal SGT.

[0138] Referring to FIG. 10, reference symbol “Psgc(n)” denotes a numberof pulses of the cam pulse signal SGC detected during a period coveringthe preceding crank angle pulse signal SGT and the current crank anglepulse signal SGT. On the other hand, reference symbol “Tsgt(n)” shown inFIG. 11 represents the period covering the preceding crank angle pulsesignal SGT and the current crank angle pulse signal SGT.

[0139] Furthermore, in FIGS. 12 to 14, reference symbol “Psgt” denotesthe number of pulses of the crank angle pulse signal SGT generated sincethe time point at which the pulse detection was started, referencesymbol “Psgc_b” denotes a number of pulses of the cam pulse signal SGCgenerated during the latest subperiod (b), reference symbol “Psgc_s(n)”denotes a number of pulses of the cam pulse signal SGC generated duringthe current subperiod (i.e., current pulse series of the generated campulse signal SGC), reference symbol “Psgc_a” denotes a number of pulsesof the cam pulse signal SGC generated during the latest subperiod (a),and reference symbol “Psgc_s(n)” denotes a number of pulses of the campulse signal SGC generated during the current pulse subperiod (i.e.,current series of the generated cam pulse signal SGC).

[0140] Now referring to FIG. 10, the pulse signal sequential orderstorage means 11 and the pulse signal number storage means 12 respond togeneration of pulse of the cam pulse signal SGC to thereby store thenumber Psgc(n) (=1) generated pulses of the cam pulse signal SGC incorrespondence with the current pulse detection period Tsgt(n) for thecrank angle pulse signal SGT (step S1).

[0141] Further, referring to FIG. 11, upon every pulse detection of thecrank angle pulse signal SGT, the pulse signal sequential order storagemeans 11 and the pulse signal number storage means 12 shift the currentpulse detection period Tsgt(n) to the preceding pulse detection periodTsgt(n−1) in a step S10 and thereafter determines arithmetically thelatest pulse detection period Tsgt(n) in a step S11, whereon theprocessing proceeds to the processing flow shown in FIG. 12.

[0142] Referring to FIG. 12, the detected pulse number Psgt of the crankangle pulse signal SGT is incremented (counted) in a step S12, whereondecision is made as to whether or not detection of the tooth dropoutposition has already been completed by referencing the tooth dropoutdetection flag in a step S13.

[0143] When it is decided in the step S13 that the tooth dropoutposition has already been detected (i.e., when the decision step S13results in affirmation “YES”), the processing makes transition to theprocessing flow (step S24) which will hereinafter be described byreference to FIG. 13. On the other hand, when it is decided in the stepS13 that no tooth dropout position has been detected (i.e., when thedecision step S13 results in negation “NO”), then decision is made as towhether or not the current crank angle position corresponds to the toothdropout position in a step S14.

[0144] More specifically, decision is made as to whether or not theperiod ratio TR,(n) of the crank angle pulse signal SGT determined inaccordance with the expression (1) mentioned hereinbefore is greaterthan the predetermined value Kr inclusive. When the decision results inthat TR(n)<Kr (i.e., “NO”), the processing proceeds to a step S23 whichwill be described later on.

[0145] On the other hand, when it is decided in the step S14 thatTR(n)≧Kr (i.e., when the decision step S14 results in affirmation“YES”), the flag indicating the end of dropout tooth detection is set ina step S15, whereon the current crank angle position A35 correspondingto the position of the dropout tooth is set (step S16).

[0146] In succession, decision is made whether the number Psgt of pulsesof the crank angle pulse signal SGT detected since the detection starttime point up to the current time point is equal to or greater than “13”with a view to determining whether or not the signal detection has beenstarted from the start point (B95) of the subperiod (b) or an earliertime point (step S17).

[0147] When the decision step S17 results in that Psgt<13 (i.e.,negation “NO”), the processing proceeds to a step S23. On the contrary,when the decision step S17 results in that Psgt>13 (i.e., affirmation“YES”), the number of the pulses Psgc_b of the cam pulse signal SGCgenerated during the subperiod (b) is verified in a step S18.

[0148] In this conjunction, the generated pulse number Psgc_b can bedetermined by accumulating or summing nine data values determinedarithmetically in the step S1 (FIG. 10) and stored before the time pointcorresponding to the position B05 in accordance with the followingexpression (2): $\begin{matrix}{{Psgc\_ b} = {{{Psgc}\quad \left( {n - 11} \right)} + {{Psgc}\quad \left( {n - 10} \right)} + \ldots + {{Psgn}\quad \left( {n - 3} \right)}}} & (2)\end{matrix}$

[0149] Subsequently, the generated pulse number Psgc_b determined inaccordance with the above expression (2) is stored as the generatedpulse number Psgc_s(n) of the current series in a step S19, which isthen followed by a decision step S20 for deciding which of the values“0”, “1” and “2” the generated pulse number Psgc_b assumes.

[0150] When it is decided that Psgc_b=“1” in the step S20, theprocessing proceeds to a step S23 because the cylinder identification isimpossible on the basis of only the value “1”.

[0151] On the other hand, when the decision step S20 results in thatPsgc_b=“0” or Psgc_b=“2”, the cylinder (cylinder #1 or cylinder #4)whose crank angle position is currently at A35 is confirmed foridentification on the basis of the table (not shown) only for thesubperiod (b) in a step S21, whereon the flag indicating the end of thecylinder identification processing is set in a step S22.

[0152] Subsequently, the generated pulse number Psgc(n−k) of the campulse signal SGC detected during the pulse period of the crank anglepulse signal SGT before k pulses (corresponding to magnitude ofdeviation of the detection start point from the subperiod start point orthe end point) is shifted to the value Psgc(n−k−1) before (k+1) pulses,whereon the pulse number Psgc(n) is cleared to zero (step S23). Theprocessing routine shown in FIG. 12 then comes to an end.

[0153] On the other hand, when it is decided in the step S13 that thetooth dropout detection end flag has already been set, indicating thatdetection of the tooth dropout position has already been completed(i.e., when the decision step S13 results in affirmation “YES”), thenthe processing proceeds to a step S24 shown in FIG. 13.

[0154] Referring to FIG. 13, in the step S24, the crank angle positionis firstly updated by 10° CA (corresponding to one period) on the basisof the number of pulses of the crank angle pulse signal SGT detectedsince the time point corresponding to the reference position A35 tothereby confirm or verify the current crank angle position, which isthen followed by a step S25 where decision is made as to whether or notthe current crank angle position has reached the succeeding positionB05.

[0155] When it is decided in the step S25 that the current crank angleposition has reached the position B05 (i.e., when the decision step S25results in “YES”), the processing proceeds to the routine shown in FIG.14, as will be described hereinafter (step S36). On the other hand,unless the current crank position has reached the position B05 (i.e.,when the decision step S25 results in “NO”), then it is decided in astep S26 whether or not the current crank position has reached theposition B95.

[0156] In case the decision in the step S26 results in that the numberof pulses of the cam pulse signal SGC detected since the position A35 isnot greater than “5”, indicating that the current crank position has notreached the position B95 yet (i.e., when the decision step S26 resultsin “NO”), the processing proceeds to the step S23 shown in FIG. 12,whereon the current processing comes to an end.

[0157] By contrast, when it is decided in the step S26 that the currentcrank position is B95 (i.e., when the decision step S26 results in“YES”), then decision is made as to whether or not the number (Psgt) ofpulses of the crank angle pulse signal SGT detected since the start ofsignal detection is greater than “9” (step S27).

[0158] When it is found in the step S27 that Psgt<9 (i.e., when thedecision step S27 results in “NO”), the processing proceeds to the stepS23 shown in FIG. 12. Thus, the current processing comes to an end.

[0159] On the other hand, when the decision step S27 results in thatPsgt≧9 (i.e., “YES”), the generated pulse number Psgc_s(n) of thecurrent cam pulse signal SGC is shifted to the preceding valuePsgc_s(n−1) in a step S28, whereon the pulse number Psgc_a of the campulse signal SGC generated during the subperiod (a) is verified in astep S29.

[0160] In this conjunction, the generated pulse number Psgc_a can bedetermined by accumulating or summing seven data values determinedarithmetically in the step S1 (FIG. 10) and stored before the time pointcorresponding to the position B95 in accordance with the followingexpression (3): $\begin{matrix}{{Psgc\_ a} = {{{Psgc}\quad \left( {n - 7} \right)} + {{Psgc}\quad \left( {n - 6} \right)} + \ldots + {{Psgc}\quad \left( {n - 1} \right)}}} & (3)\end{matrix}$

[0161] Subsequently, the generated pulse number Psgc_a determined inaccordance with the above expression (3) is stored as the current seriesof generated pulse number Psgc_s(n) in a step S30, whereon it is decidedin a step S31 whether or not detection of the pulse number Psgc_bgenerated during the preceding latest subperiod (b) (i.e., the precedingseries of value Psgc_s(n−1)) has been terminated.

[0162] When it is decided in the step S31 that detection of the pulsenumber Psgc_b generated during the subperiod (b) has already beenterminated (i.e., when the decision step S31 results in “YES”), thecylinder proper to the current crank angle position is confirmed orverified on the basis of combination of the generated pulse numberPsgc_b and the number of pulses generated during the current subperiod(a), i.e., pulse number Psgc_a, by referencing the cylinderidentification table for the subperiods (b) and (a) in a step S32 (seeFIG. 6), whereon the processing proceeds to a step S35 described lateron.

[0163] On the contrary, when it is decided in the step S31 thatdetection of the pulse number Psgc_b generated during the precedingsubperiod (b) has not been completed yet (i.e., when the decision stepS31 results in “NO”), decision is then made as to which of the values of“0”, “1” and “2” the number of pulses Psgc_a generated during thecurrent subperiod (a) assumes (step S33).

[0164] When it is decided that Psgc_(—a=“)0” in the step S33, theprocessing proceeds to the step S23 shown in FIG. 12 because thecylinder identification is impossible on the basis of only the value“0”, whereon the processing comes to an end.

[0165] On the other hand, when the decision step S33 results in thatPsgc_a=“1” or Psgc_(—a=“)2”, the cylinder (cylinder #1 or cylinder #3)whose crank angle position is currently B95 is confirmed foridentification on the basis of the table (not shown) only for thesubperiod (a) in a step S34, whereon the flag indicating the end of thecylinder identification processing is set in a step S35. In succession,the processing proceeds to the step S23 shown in FIG. 12.

[0166] On the other hand, when it is decided in the step S25 that thecurrent crank angle position is B05, (i.e., when the decision step S25results in “YES”), then the processing proceeds to a step S36 shown inFIG. 14.

[0167] Referring to FIG. 14, the current series of the generated pulsenumber Psgc_s(n) of the cam pulse signal SGC is firstly shifted to thepreceding value Psgc_s(n−1) in the step S36, whereon the pulse numberPsgc_b of the cam pulse signal SGC generated during the subperiod (b) isverified in a step S37.

[0168] In this conjunction, the generated pulse number Psgc_b can bedetermined by accumulating or summing nine data values determinedarithmetically in the step S1 (FIG. 10) and stored before the time pointcorresponding to the position B05 in accordance with the followingexpression (4): $\begin{matrix}{{Psgc\_ b} = {{{Psgc}\quad \left( {n - 8} \right)} + {{Psgc}\quad \left( {n - 7} \right)} + \ldots + {{Psgc}\quad (n)}}} & (4)\end{matrix}$

[0169] Subsequently, the generated pulse number Psgc_b determined inaccordance with the above expression (3) is stored as the current seriesof generated pulse number Psgc_s(n) in a step S38, whereon it is decidedin a step S39 whether or not detection of the pulse number Psgc_agenerated during the preceding latest subperiod (a) (i.e., the precedingseries of value Psgc_s(n−1)) has been completed.

[0170] When it is decided in the step S39 that detection of the pulsenumber Psgc_a generated during the subperiod (a) has already beencompleted (i.e., when the decision step S39 results in “YES”), thecylinder proper to the current crank angle position is confirmed orverified on the basis of combination of the generated pulse numberPsgc_a and the number of pulses generated during the current subperiod(b), i.e., pulse number Psgc_b, by verifying the cylinder identificationtable for the subperiods (a) and (b) in a step S40 (see FIG. 4), whereonthe processing proceeds to a step S43 described later on.

[0171] On the contrary, when it is decided in the step S39 thatdetection of the pulse number Psgc_a generated during the precedingsubperiod (a) has not been completed yet (i.e., when the decision stepS39 results in “NO”), decision is then made as to which value of “0”,“1” and “2” the number of pulses Psgc_b generated during the currentsubperiod (b) is (step S41).

[0172] When it is decided that Psgc_b=“1” in the step S41, theprocessing proceeds to the step S23 shown in FIG. 12 because thecylinder identification is impossible on the basis of only the value“1”, whereon the processing comes to an end.

[0173] On the other hand, when the decision step S41 results in thatPsgc_b=“0” or Psgc_b=“2”, the cylinder (cylinder #1 or cylinder #4)whose crank angle position is currently B05 is confirmed foridentification on the basis of the table (not shown) only for thesubperiod (b) in a step S42, whereon the flag indicating the end of thecylinder identification processing is set (step S43). In succession, theprocessing proceeds to the step S23 shown in FIG. 12.

[0174] As is apparent from the foregoing, according to the teachings ofthe present invention incarnated in the first embodiment thereof, thecylinder identification can be achieved during a shorter period crankangle rotation than the conventional system independently of the signaldetection start timing upon starting of engine operation on the basis ofthe number of pulses of the cam pulse signal SGC generated during onlythe subperiod (a) or subperiod (b) or the combination of the pulsenumbers generated during the subperiods (a) and (b) in this order or thecombination of the pulse numbers generated during the subperiods (b) and(a).

[0175] By way of example, when the crank angle pulse signal SGT has beendetected from a time point before the start point of the precedingsubperiod (b) upon detection of the reference position A35, it can bedetermined that the current cylinder is the cylinder #4 on the basis ofthe pulse number “2” of the cam pulse signal SGC generated during thepreceding subperiod (b).

[0176] Further, when the crank angle pulse signal SGT has been detectedfrom a time point preceding to the start point of the current subperiod(a) upon detection of the end point of the current subperiod (a)including the position A35 in succession to the detection of thereference position A35, the cylinder #1 or cylinder #3 can be identifiedin dependence on the pulse number “1” or “2” of the cam pulse signal SGCgenerated during the current subperiod (a).

[0177] Furthermore, when the crank angle pulse signal SGT has beendetected from a time point before the start point of the precedingsubperiod upon detection of the end points of plural subperiodssuccessively, the cylinder identification can be realized on the basisof the combination of the pulse numbers of the cam pulse signal SGCgenerated during the preceding subperiod and the current subperiod,respectively.

[0178] In other words, by discriminating the subperiod in which thereference position A35 is included and determining speedily whetherdetection of the pulses of the cam pulse signal SGC has been startedbefore the start point of the subperiod (a) or the subperiod (b) upondetection of the reference position A35 (tooth dropout position) of thecrank angle pulse signal SGT, the cylinder identification can beaccomplished swiftly on the basis of the number of pulses of the campulse signal SGC generated during the determined or confirmed subperiodsor combination thereof.

[0179] Thus, the cylinder identification can be performed immediatelyupon termination of the detection period including plural subperiodsrequired for the cylinder identification. This means that the range ofthe crank angle and thence the time taken for the cylinderidentification can be reduced with the time duration of the enginestarting operation up to transition to the ordinary ignition controlmode being shortened correspondingly.

[0180] In this conjunction, it should be noted that correspondencesbetween the combinations of the generated pulse numbers (“0”, “1” and“2”) of the cam pulse signal SGC and the individual cylinders can beestablished with high reliability because the pulse number combinationsare so set as to differ from one to another subperiod, as can be seen inFIG. 2.

[0181] Furthermore, owing to the arrangement such that the generatedpulse number combination of “0” and “0” of the cam pulse signal SGC cannever occur during the plural subperiods for cylinder identification,erroneous or false cylinder identification can be evaded even uponoccurrence of a fault such as wire breakage, whereby the fail-safefunction can be protected from being impaired.

[0182] Parenthetically, in the case where the cylinder identification isperformed on the basis of the table data only for the subperiod (b) (seeFIG. 12, steps S20 and 21), identification of the proper cylinder can bevalidated in the case where the pulse number Psgc_b of the cam pulsesignal SGC generated during the subperiod (b) is “0” or alternatively“2”. By contrast, when the pulse number Psgc_b is “0”, discriminationfrom the wire breakage fault is rendered impossible. Accordingly, inthis case, the cylinder identification processing may be so arranged asto be inhibited.

[0183] It should further be added that since the sequential relation ofthe timings at which the crank angle pulse signal SGT and the cam pulsesignal SGC are generated are stored as the history data in the storagemeans 11 and 12 incorporated in the cylinder identifying means 10together with the detected pulse numbers of the crank angle pulse signalSGT and the cam pulse signal SGC from the time point when the engineoperation is started, high reliability can be ensured for the cylinderidentification.

[0184] Besides, because the crank angle pulse signal SGT is representedby a pulse train in which individual pulses make appearance periodicallyat an interval corresponding to 10° CA, the crank angle positionsdesignated discriminatively by the individual pulses can be determinedwith high accuracy, ensuring enhanced reliability and accuracy forcylinder control.

[0185] Additionally, owing to the feature that the reference positionindicated by the pulse included in the crank angle pulse signal SGT isset at the crank angle of A35 and that the tooth dropout position is setat the position corresponding to the crank angle of tooth dropoutposition A25 which bears low degree of relevancy to the engine controlreference position, any appreciable influence will never be exerted tothe control of the individual cylinder operations.

[0186] Finally, it should be added that the number of divisions of theTDC period as well as the order of the generated pulse numbers of thecam pulse signal SGC on the subperiod basis is never restricted to theexample illustrated in FIG. 2 but may be so arranged that the generatedpulse number of the cam pulse signal SGC differs from one to anothercylinder. In other words, the cylinder discrimination can be realizedwithin a short time as in the case of the illustrated embodiment byadopting the pulse number combination of the cam pulse signalsappropriate for a given number of the subperiods, needless to say.

[0187] Embodiment 2

[0188] The foregoing description directed to the first embodiment of thepresent invention has been made on the presumption that the invention isapplied to the four-cylinder internal combustion engine. A secondembodiment of the present invention is concerned with the cylinderidentifying system which can be applied to a six-cylinder internalcombustion engine substantially to the same advantageous effect.

[0189]FIG. 15 is a timing chart showing pulse generation patterns of thecrank angle pulse signal SGT and the cam pulse signal SGC generated inthe cylinder identifying system according to the second embodiment ofthe invention applied to the six-cylinder engine. Referring to FIG. 15,the tooth dropout position is set at the crank position A25, as in thecase of the first embodiment. However, in the six-cylinder internalcombustion engine, the TDC period (i.e., ignition control subperiod)extends over 120° CA. Consequently, the subperiod (a) ranges from B05 toB65° CA (hereinafter referred simply to as the “B65”) while thesubperiod (b) ranges from B65 to B05.

[0190]FIG. 16 is a timing chart for illustrating, by way of example, thecylinder identifying operation carried out by the cylinder identifyingsystem according to the instant embodiment of the present invention onthe presumption that the detection of the crank angle pulse signal SGThas been started from a time point immediately preceding to the startpoint (B05) of the subperiod (a).

[0191]FIG. 17 is a view showing a cylinder identification table to bereferenced in conjunction with the signal detection pattern illustratedin FIG. 16. As can be seen in FIG. 17, it is presumed that the signaldetection is started from the position B05 of the cylinder #6 fordetermining discriminatively the crank position B05 for the cylinder #1on the basis of combination of the numbers of the pulses “1” and “0”generated during the subperiods (a) and (b), respectively, at the timepoint when the succeeding crank position B05 is detected.

[0192] The signal detection pattern sown in FIG. 16 differs from thatshown in FIG. 3 only in the respect that the TDC period extends over120° CA. Except for this, the basic cylinder identifying operation isessentially same as that of the cylinder identifying system according tothe first embodiment of the invention described hereinbefore.Accordingly, detailed description of the cylinder identifying operationof the cylinder identifying system according to the instant embodimentof the present invention will be unnecessary. It should however be notedthat the time taken for the cylinder identification corresponds to thecrank rotation angle of 120° CA.

[0193]FIG. 18 is a timing chart for illustrating another example of thecylinder identifying operation carried out by the cylinder identifyingsystem according to the instant embodiment of the present invention onthe presumption that the detection of the crank angle pulse signal SGThas been started from a time point immediately preceding to the startpoint (B65) of the subperiod (b).

[0194]FIG. 19 is a view showing a cylinder identification table to bereferenced in conjunction with the signal detection pattern illustratedin FIG. 18. As can be seen in FIG. 19, it is presumed that the signaldetection is started from the position B65 of the cylinder #2 fordetermining discriminatively the crank position B65 for the cylinder #3on the basis of combination of the numbers of the pulses “0” and “1”generated during the subperiods (b) and (a), respectively, at the timepoint when the succeeding crank position B65 is detected. Also in thecase of the signal detection pattern shown in FIG. 18, the time takenfor the cylinder identification corresponds to the crank rotation angleof 120° CA.

[0195]FIG. 20 shows a timing chart in the case where the crank anglepulse signal SGT has been detected immediately after the start point(B55° CA) of the subperiod (b). In the case of the example illustratedin FIG. 20, the number of pulses generated during the first subperiod(b) can not be checked or confirmed. Nevertheless, it is possible toidentify the position B05 of the cylinder #4 on the basis of the numbersof pulses “0” and “2” generated during the succeeding subperiods (a) and(b) by referencing the table illustrated in FIG. 17. In this case, thetime involved for the cylinder identification corresponds to the crankrotation angle of 180° CA.

[0196] Further, FIG. 21 shows a timing chart in the case where the crankangle pulse signal SGT has been detected immediately after the startpoint (A05° CA) of the subperiod (a). In the case of the exampleillustrated in FIG. 21, the number of pulses generated during the firstsubperiod (a) can not be checked or confirmed. Nevertheless, it ispossible to identify the position B65 of the cylinder #6 on the basis ofthe numbers of pulses “1” and “0” generated during the succeedingsubperiods (b) and (a) by referencing the table illustrated in FIG. 19.Also in this case, the time involved for the cylinder identificationcorresponds to the crank rotation angle of 180° CA.

[0197] Further, FIG. 22 is a view showing, by way of example, a tableemployed for reference in the ordinary cylinder identification. In thisordinary cylinder identification, the numbers of pulses generated duringthe subperiod (a) and the subperiod (b) are totalized on acylinder-by-cylinder basis, whereon the cylinder identification isperformed by referencing the generated pulse number of the cam pulsesignal SGC during the TDC subperiod.

[0198] Embodiment 3

[0199] In the case of the second embodiment of the present invention,the cylinder identifying system is applied to the six-cylinder internalcombustion engine. A third embodiment of the present invention isdirected to the cylinder identifying system applied to a three-cylinderinternal combustion engine for realizing the similar advantageouseffects as those mentioned hereinbefore.

[0200]FIG. 23 is a timing chart showing pulse generation patterns of thecrank angle pulse signal SGT and the cam pulse signal SGC generated inthe cylinder identifying system according to the third embodiment of theinvention applied to the three-cylinder engine. Referring to FIG. 23,the tooth dropout position is set at the crank position A25, as in thecase of the first and second embodiments. However, in the three-cylinderinternal combustion engine, the TDC period (i.e., ignition controlsubperiod) extends over 240° CA.

[0201] Since multiplication of the TDC period by an integral number doesnot result in 360° CA, substantially same crank angle pulse signal SGTas that employed in the cylinder identifying system for the six-cylinderengine described in Conjunction with the second embodiment of theinvention is employed, wherein the tooth dropout position is set at A25and B95, respectively.

[0202] More specifically, in the cylinder identifying system for thethree-cylinder engine, it is impossible to set one reference positionfor each cylinder during one cycle (720° CA) of the engine. Accordingly,a pair of tooth dropout positions A25 and B95 are set for every TDCperiod (240° CA).

[0203] In this case, each TDC period is divided into two subperiods,i.e., subperiod (a); subperiod (b). FIGS. 24 and 25 are views showingcylinder identification tables referenced in operation of the cylinderidentifying system according to the instant embodiment of the presentinvention.

[0204] The table shown in FIG. 24 is employed for reference inperforming the cylinder identification on the basis of the generatedpulse number of the cam pulse signal SGC during the subperiod (a) andsubperiod (b), wile the table shown in FIG. 25 is employed for referencein performing the cylinder identification on the basis of the generatedpulse number of the cam pulse signal SGC during the subperiod (b) andsubperiod (a).

[0205] Now, it can be seen that the cylinder can be identified at anearlier time point regardless of the position of the detection startingcrank angle in the engine start operation mode, whereby the time takenfor stating the engine operation can be shortened. In other words,engine starting performance can significantly be enhanced.

[0206] Furthermore, through the plural subperiods employed for thecylinder identification, the combinations of the pulse numbers generatedfor every subperiods over the plural subperiods used for the cylinderidentification can never assume “0” and “0”. Thus, it can be said thatthe cylinder identifying system according to the instant embodiment ofthe invention is excellent in respect to fail-safe performance.

[0207] Many features and advantages of the present invention areapparent from the detailed description and thus it is intended by theappended claims to cover all such features and advantages of the systemwhich fall within the true spirit and scope of the invention. Further,since numerous modifications and combinations will readily occur tothose skilled in the art, it is not intended to limit the invention tothe exact construction and operation illustrated and described.

[0208] Accordingly, all suitable modifications and equivalents may beresorted to, falling within the spirit and scope of the invention.

What is claimed is:
 1. A cylinder identifying system for an internal combustion engine, comprising: crank angle signal detecting means for generating a crank angle pulse signal composed of pulse trains each containing a reference position in synchronism with rotation of a crank shaft of said internal combustion engine; a cam shaft rotating at a speed corresponding to one half of that of said crank shaft; cam signal detecting means for generating a cam pulse signal including specific pulses identifying individual cylinders, respectively, of said internal combustion engine in synchronism with rotation of said cam shaft; and cylinder identifying means for identifying said individual cylinders, respectively, of said internal combustion engine on the basis of said crank angle pulse signal and said cam pulse signal, wherein said cylinder identifying means includes: pulse signal number storage means for dividing an ignition control period for each of said individual cylinders into a plurality of subperiods for thereby counting for storage signal numbers of said specific pulses generated during said plurality of subperiods, respectively; and subperiod discriminating means for determining discriminatively a sequential order of said plural subperiods on the basis of combinations of the signal numbers of said specific pulses generated during said plural subperiods, respectively, wherein said combinations of the signal numbers of said specific pulses generated during said plural subperiods differ from one to another correspondingly to said plural subperiods in dependence on start points of said plural subperiods, respectively, and wherein said cylinder identifying means is so designed as to identify said individual cylinders on the basis of results of said discriminative determination of said subperiods performed by said subperiod discriminating means independently of the start points of said plural subperiods.
 2. A cylinder identifying system for an internal combustion engine according to claim 1, wherein said pulse signal number storage means is so designed as to count for storage the numbers of pulses of said cam pulse signal and said crank angle pulse signal, respectively, from the start of operation of said internal combustion engine, wherein said cylinder identifying means includes: pulse signal sequential order storage means for storing therein temporal relations between said pulse trains of said crank angle pulse signal and said specific pulses of said cam pulse signal; and reference position detecting means for detecting said reference position from said crank angle pulse signal, wherein when it is decided that said crank angle pulse signal has been detected since a start point of a preceding one of said plural subperiods at the latest on the basis of the number of pulses of said crank angle pulse signal which have been stored up to said reference position, said cylinder identifying means identifies said individual cylinders on the basis of the signal number of said cam pulse signal(s) generated during said preceding subperiod.
 3. A cylinder identifying system for an internal combustion engine according to claim 2, wherein when decision is made after detection of said reference position that said crank angle pulse signal has been detected since the start point of a current one of said plural subperiods at the latest on the basis of the pulse number of said crank angle pulse signal stored up to a time point at which an end point of said current subperiod including said reference position is detected, said cylinder identifying means identifies the individual cylinders on the basis of the signal number of said cam pulse signal(s) generated during said current subperiod.
 4. A cylinder identifying system for an internal combustion engine according to claim 2, wherein when it is decided on the basis of the pulse number of said crank angle pulse signal stored up to a subperiod end point of said plural subperiods that said crank angle pulse signal has been detected since the start point of said preceding subperiod at the latest, said cylinder identifying means identifies said individual cylinders on the basis of combination of the signal number of said cam pulse signal(s) generated during the preceding subperiod and the signal number of said cam pulse signal(s) generated during the current subperiod.
 5. A cylinder identifying system for an internal combustion engine according to claim 1, wherein combination of signal numbers of said cam pulse signal(s) generated during said plural subperiods contains no combination of only “0s” which indicates absence of output.
 6. A cylinder identifying system for an internal combustion engine according to claim 5, wherein number of the cylinders of said internal combustion engine is four with the ignition control period for each of said cylinders being so set as to correspond to a crank angle of 180°, said plural subperiods being constituted by a first subperiod and a second subperiod, and wherein numbers of said specific pulses contained in said cam pulse signal generated during said first subperiod and said second subperiod, respectively, are “1” and “0”, “2” and “1”, “0” and “2” and “0” and “1”, respectively, in the order in which said cylinders are to be controlled.
 7. A cylinder identifying system for an internal combustion engine according to claim 5, wherein number of the cylinders of said internal combustion engine is six with the ignition control period for each of said cylinders being so set as to correspond to a crank angle of 120°, said plural subperiods being constituted by a first subperiod and a second subperiod, and wherein numbers of said specific pulses contained in said cam pulse signal generated during said first subperiod and said second subperiod, respectively, are “1” and “0”, “2” and “0”, “1” and “2”, “0” and “2”, “1” and “1” and “0” and “1”, respectively, in the order in which said cylinders are to be controlled.
 8. A cylinder identifying system for an internal combustion engine according to claim 5, wherein number of the cylinders of said internal combustion engine is three with the ignition control period for each of said cylinders being so set as to correspond to a crank angle of 240°, said plural subperiods being constituted by a first subperiod and a second subperiod, and wherein numbers of said specific pulses contained in said cam pulse signal generated during said first subperiod and said second subperiod, respectively, are “1” and “0”, “2” and “0”, “1” and “2”, “0” and “2”, “1” and “1” and “0” and “1”, respectively, in the order in which said cylinders are to be controlled.
 9. A cylinder identifying system for an internal combustion engine according to claim 6, wherein said crank angle pulse signal is composed of pulse trains each of a period corresponding to a crank angle of 10°, and wherein said reference position included in said crank angle pulse signal is set at a crank angle of 35° from a top dead center on a cylinder-by-cylinder basis. 